The present invention relates to medical instruments and devices; and in particular to endoscopes, guidewires, retrieval devices, and similar tools often used alone or in combination for minimally invasive medical procedures.
An endoscope is a medical instrument used to inspect the inside of the body. A typical endoscope has a distal end comprising an optical or electronic imaging system, a proximal end with controls for manipulating the endoscope, a rigid or flexible tubular, elongate shaft connecting the ends, and a steering means to control the deflection of the distal end. Often, the steering mechanism includes a complicated set of mechanical linkages within the shaft. To use an endoscope, the physician inserts the distal end into the patient through a natural orifice or an artificial incision, pushes the shaft into the patient, monitors the progress of the distal end inside the patient by watching the acquired image, and controls the angle of view and the direction of progress by the steering mechanism in order to maneuver the distal end to the site of interest. The proximal end remains outside the patient, where it is connected to an eyepiece, video monitor, or other equipment, for example, to display the acquired image.
Some endoscopes are inspection devices not used for remote procedures. Other endoscopes let a physician, surgeon, or medical technician pass tools or treatments through a lumen, called a “working channel,” that runs lengthwise within the endoscope shaft. The physician often uses the working channel to tools or other instruments, called “functional elements,” into the patient, for example, to perform endoscopic surgical procedures. A tool often used in conjunction with an endoscope is a retrieval device, typically used to capture and extract objects, such as stones or foreign bodies, or to resect and extract tissue, such as polyps or biopsy samples. A typical retrieval device comprises a distal end having a retrieval basket formed from one or more wire loops and a proximally extending shaft having a filamentous construction of one or more bundled wires. The basket and shaft may be slideably disposed in a sheath, which is usually a thin-walled, flexible polymer tube. Typically, the basket is resiliently collapsible as its shaft is drawn proximally into its sheath via a slide actuator in a handle at the proximal end.
To use a retrieval device, the physician first inserts a general-purpose endoscope into the patient and guides it to the site of interest. The physician then inserts the distal end of the retrieval device into the proximal end of the working channel and pushes the retrieval device down the channel until it emerges from the distal end, so that the distal end of the retrieval device becomes visible through the endoscope. The physician can then watch the endoscope image of the retrieval device in order to guide the device to the object of interest; maneuver the open basket to surround the object; collapse the basket via the slide actuator to trap the object; and withdraw the device back up the working channel to extract the object from the patient. Because the retrieval device does not provide for image acquisition or for guiding the device to a target site within the patient's body, the procedure requires two major components: an endoscope (for steering and imaging) and a retrieval device (for guiding and extracting).
Another medical instrument, sometimes used with an endoscope but also used independently, is a guidewire. In essence, a guidewire is a filament or group of filaments inserted into to the body, typically to facilitate emplacement of a medical device. For example, the physician inserts the guidewire through a natural orifice or an artificial incision, advances the guidewire to a site of interest, slips a catheter (for example) over the guidewire, advances the catheter over the guidewire, and then withdraws the guidewire, leaving the catheter in place. To gauge the location of a conventional guidewire within the body, the physician relies on feel, fluoroscopy, or endoscopic imaging. To aid in manipulating the guidewire, the physician may grasp it with a torque handle or similar device, which is removable to facilitate passing the catheter (for example) over the guidewire.
Using a general-purpose endoscope as a “host” to insert a second, specialized tool such as a guidewire or a retrieval device creates a complex system with several drawbacks. One problem with the conventional approach is that general-purpose endoscopes are expensive instruments with relatively short lifetimes and high maintenance costs. Using a general-purpose endoscope for specialized, recurring tasks exposes it to wear and tear, for example, during cleaning, sterilization, handling, and use.
A second problem relates to the ongoing goal of reducing the diameter of endoscopic surgical instruments. A major benefit of endoscopic surgery is that an endoscopic procedure is usually far less invasive than its traditional surgical alternative. That said, inserting an endoscope and guiding it to the site of interest can be an uncomfortable and upsetting experience for the patient. Cystoscopy, for example, is a procedure for inspecting of the interior of the bladder. A physician may perform cystoscopy in an office setting with the patient awake. The physician typically gives the patent a local anesthetic and then inserts a type of endoscope called a cystoscope up the patient's urethra and into the bladder. For the patient, this procedure can be physically and mentally uncomfortable. The amount of discomfort depends on, among other things, the diameter of the cystoscope. Existing cystoscopes have a diameter of about 16 French—which is more than 5 mm. Reducing this diameter would improve patient comfort by reducing the amount of urethral dilation during cystoscopy.
The benefits of smaller-diameter endoscopic instruments generalize from cystoscopes to endoscopic instruments as a class. In addition to reducing discomfort, smaller endoscopic instruments also reduce the invasiveness of endoscopic procedures, especially for those requiring an artificial incision. A smaller instrument requires a smaller incision, contributing to faster recovery, reduced scarring, and a lower risk of complications—and therefore to a lower average cost per procedure. Smaller instruments also extend the range of procedures that can be accomplished endoscopically, enhancing the utility of endoscopic instruments and reducing the need for conventional surgery. Smaller diameter endoscopic instruments are always a welcome addition to the art.